Engineering topics

Condon, E. P.

Publications and source records attributed to Condon, E. P..

18 records

NASA NTRS1990

Aircraft measurements of NO(x) over the eastern Pacific and continental United States and implications for ozone production

Results are reported from airborne measurements of NO, NO2, O3, and CO obtained in the free troposphere (FT) and boundary layer (BL) over the western U.S. and eastern Pacific during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) in summer 1986. The aircraft instrumentation and the CITE 2 flight protocols are described, and the results are presented in extensive tables and graphs. Over the ocean the median mixing ratios for NO and NO2 were found to be 4.0 and 10.4 parts per trillion by volume (pptv), respectively, in the BL and 12.4 and 18.0 pptv in the FT; the corresponding values over land were 34.5 and 75.0 pptv in the BL and 13.0 and 36.0 pptv in the FT. in continental air masses. NO(x) is shown to be positively correlated with O3 and CO and negatively correlated with dewpoint over the ocean, whereas over land NO(x) was positively correlated with O3, CO, and dewpoint.

Carroll, M. A.↗

NASA NTRS1989

The planning and execution of ER-2 and DC-8 aircraft flights over Antarctica, August and September 1987

The significant ozone loss in the lower stratosphere over Antarctica during recent austral springs was studied by instrumented ER-2 and DC-8 aircraft. Data on the homogeneous gas composition, polar stratospheric clouds, and on tracers for dynamic motion are provided. The mission design is described, the aircraft and their payloads are documented, and the flight tracks are specified.

Tuck, A. F.↗

NASA NTRS1989

Measurements of NO(x) over the eastern Pacific Ocean and southwestern United States during the spring 1984 NASA GTE aircraft program

Measurements of NO, NO(x) (NO + NO2), O3, and CO are presented from seven aircraft flights made over the eastern Pacific Ocean and the southwestern United States in spring of 1984. The sampling region was characterized by large- and small-scale variability for all of the measurements, likely as a result of vigorous synoptic scale meteorology and the influence of tropopause folds. Median values for NO, NO(x), O3, and CO from the flights made over the ocean in the region of 5.8-7.6 km were 10 parts per trillion by volume (pptv), 32 pptv, 46 parts per billion by volume (ppbv), and 120 ppbv, respectively. Corresponding values from two flights made over the continent at similar altitudes were 16 pptv, 38 pptv, 42 ppbv, and 111 ppbv. There was a strong tendency for NO or NO(x) to be correlated positively with O3 and to be anticorrelated with dew-point/frost-point measurements. No significant overall correlation occurred between NO(x) and CO for the ocean data. The variability of NO(x) was such that regions of net destruction and regions of net production of O(3) were sampled both over the ocean and over the continent. However, in the middle free troposphere over the ocean, net O(3) destruction was predominant.

Ridley, B. A.↗

NASA NTRS1988

An intercomparison of results from ferrous sulphate and photolytic converter techniques for measurements of NO(x) made during the NASA GTE/CITE 1 aircraft program

Two techniques designed for measurements of NO(x (NO + NO2) were intercompared during aircraft flights made in the spring of 1984 in the middle free troposphere over the eastern Pacific Ocean and southwestern U.S. One NO chemiluminescence instrument was equipped with a ferrous sulphate converter, another with a photolytic converter. The ferrous sulphate-equipped instrument was apparently much less specific for NO2. It registered levels about three times larger than the photolytic converter and gave NO2/NO ratios that were much larger than photochemical calculations would indicate as reasonable. Additionally, the results imply that active NO(x) was only 10-20 percent of the total odd nitrogen in the middle free troposphere.

Ridley, B. A.↗

NASA NTRS1986

Gas filter radiometer for carbon monoxide measurements during the 1979 Summer Monsoon Experiment (MONEX)

The instrumental and data-reduction techniques used in obtaining remote measurements of carbon monoxide during the 1979 Summer Monsoon Experiment are described. The form of the signal function (the variation of signal with altitude) and the impact of variations in the vertical distribution of carbon monoxide are discussed. Estimates of the experimental accuracy are made both by assessment of error sources through the use of numerical simulations and by comparison with concurrent measurements made by means of gas chromatography. It is found that the radiometric measurements tend to be about 9 percent lower than the direct measurements and to have a precision of about 8 percent.

Reichle, H. G., Jr.↗

NASA NTRS1985

An intercomparison of carbon monoxide measurement techniques

Results from an intercomparison of techniques to measure tropospheric levels of carbon monoxide (CO) are discussed. The intercomparison was conducted as part of the National Aeronautics and Space Administration's Global Tropospheric Experiment (GTE) and was held at Wallops Island, VA, in July 1983. Instruments intercompared included a laser differential absorption method and three grab sample/gas chromatograph methods. The intercomparison consisted of simultaneous measurements of ambient levels of CO and controlled injections of CO from a common manifold. Results from the techniques exhibited a high degree of correlation among themselves and with changes in the CO mixing ratio. The results suggested a level of agreement among the techniques of about 15 percent. However, a day-to-day bias between the techniques was observed, which resulted in differences between techniques as large as 38 percent.

Hoell, J. M., Jr.↗

NASA NTRS1984

An intercomparison of carbon monoxide, nitric oxide, and hydroxyl measurement techniques - Overview of results

Results from an intercomparison of methods to measure carbon monoxide (CO), nitric oxide (NO), and the hydroxyl radical (OH) are discussed. The intercomparison was conducted at Wallops Island, Virginia, in July 1983 and included a laser differential absorption and three grab sample/gas chromatograph methods for CO, a laser-induced fluorescence (LIF) and two chemiluminescence methods for NO, and two LIF methods and a radiocarbon tracer method for OH. The intercomparison was conducted as a field measurement program involving ambient measurements of CO (150-300 ppbv) and NO (10-180 pptv) from a common manifold with controlled injection of CO in incremental steps from 20 to 500 ppbv and NO in steps from 10 to 220 pptv. Only ambient measurements of OH were made. The agreement between the techniques was on the order of 14 percent for CO and 17 percent for NO. Hardware difficulties during the OH tests resulted in a data base with insufficient data and uncertanties too large to permit a meaningful intercomposition.

Hoell, J. M.↗

NASA NTRS1984

Experimental determination of the boundary layer at air-sample inlet positions on the NASA CV 990 aircraft

Full-scale, in-flight measurements of the boundary-layer thickness, velocity profile, and flow angle have been made at several sample collection stations on the fuselage of the NASA CV 990. These results are given as functions of Mach number, Reynolds number, yaw, and angle of attack.

Bowen, S. W.↗

NASA NTRS1984

Air-sampling inlet contamination by aircraft emissions on the NASA CV-990 aircraft

Results of an experimental investigation of the contamination of air sampling inlets by aircraft emissions from the NASA CV-990 research aircraft are presented. This four-engine jet aircraft is a NASA facility used for many different atmospheric and meteorological experiments, as well as for developing spacecraft instrumentation for remote measurements. Our investigations were performed to provide information on which to base the selection of sampling locations for a series of multi-instrument missions for measuring tropospheric trace gases. The major source of contamination is the exhaust from the jet engines, which generate many of the same gases that are of interest in atmospheric chemistry, as well as other gases that may interfere with sampling measurements. The engine exhaust contains these gases in mixing ratios many orders of magnitude greater than those that occur in the clean atmosphere which the missions seek to quantify. Pressurized samples of air were collected simultaneously from a scoop located forward of the engines to represent clean air and from other multiport scoops at various aft positions on the aircraft. The air samples were analyzed in the laboratory by gas chromatography for carbon monoxide, an abundant combustion by-product. Data are presented for various scoop locations under various flight conditions.

Condon, E. P.↗

NASA NTRS1983

Measurements of stratospheric SO2 after the EL Chichon eruptions

Samples of stratospheric trace gases were obtained on eight flights of NASA high-altitude aircraft from April 16 through December 13, 1982. The sampling occurred at altitudes from 15 to 22 km, latitudes from 23 to 52 deg N, and longitudes from 108 to 130 deg W. The cryogenically concentrated samples were analyzed by gas chromatography for SO2, a primary precursor of the gas-to-particle conversion process. The measured mixing ratio of SO2 varied between 8 and 132 pptv. Evidence from aerosol measurements indicates that a few of our early samples may have been collected in the fringes of the volcanic cloud from El Chichon. Samples obtained on some later flights may have been from the eruption cloud but were taken at times when most of the volcanically injected SO2 should have been converted to H2SO4.

Vedder, J. F.↗

NASA NTRS1982

Precursor gases of aerosols in the Mount St. Helens eruption plumes at stratospheric altitudes

Nineteen stratospheric samples from the eruption plumes of Mount St. Helens were collected in five flight experiments. The plume samples were collected at various altitudes from 13.1 to 20.7 km by using the Ames cryogenic sampling system on board the NASA U-2 aircraft. The enriched, cryogenically collected samples were analyzed by chromatography. The concentrations of aerosols precursor gases (OCS, SO2, and CS2), CH3Cl, N2O, CF2Cl2, and CFCl3 were measured by gas chromatography. Large enhancement of the mixing ratio of SO2 and moderate enhancement of CS2 and OCS were found in the plume samples compared with similar measurement under pre-volcanic conditions. A fast decay rate of the SO2 mixing ratio in the plume was observed. Measurement of Cl(-), SO2(2-), and NO3(-) by ion chromatography was also carried out on water solutions prepared from the plume samples. The results obtained with this technique imply large mixing ratios of HCl, (NO + NO2 + HNO3), and SO2, in which these constituents are the respective sources of the anions. Measurement of the Rn222 concentration in the plume was made. Other stratospheric constituents in the plume samples, such as H2O, CO2, CH4, and CO, were also observed.

Inn, E. C. Y.↗

NASA NTRS1981

Measurements of CO and CH4 in the troposphere over Saudi Arabia, India, and the Arabian Sea during the 1979 International Summer Monsoon Experiment /MONEX/

During the 1979 Summer MONEX, 150 air samples collected over Saudi Arabia, India, and the Arabian Sea were analyzed for CO and CH4. Near Dhahran and over the Ganges Valley there were high concentrations of CO, around 300 ppbv, in the boundary layer. Out over the Saudi Arabian desert there was no sharp increase in the boundary layer. It is suggested that these high concentrations originate from pollution sources. Low values of CO, down to 80 ppbv, are found over the Arabian Sea as the monsoon progresses, and these may originate from the Southern Hemisphere. Methane over Saudi Arabia (1.59 ppmv) is a little higher than that over the Arabian Sea (1.54 ppmv) probably because the latter region is influenced by air from the Southern Hemisphere.

Newell, R. E.↗

NASA NTRS1981

Gaseous constituents in the plume from eruptions of Mount St. Helens

Measurements in the stratosphere of gaseous constituents in the plume of Mount St. Helens were obtained during five flights of the NASA U-2 aircraft between 19 May and 17 June 1980. Mixing ratios from gas chromatographic measurements on samples acquired about 24 hours after the initial eruption show considerable enhancement over nonvolcanic concentrations for sulfur dioxide (more than 1000 times), methyl chloride (about 10 times), and carbon disulfide (more than 3 times). The mixing ratio of carbonyl sulfide was comparable to nonvolcanic mixing ratios although 3 days later it was enhanced two to three times. Ion chromatography measurements on water-soluble constituents are also reported. Very large concentrations of chloride, nitrate, and sulfate ions were measured, implying large mixing ratios for the water-soluble gaseous constituents from which the anions are derived. Measurements of radon-222 present in the plume are also reported.

Inn, E. C. Y.↗

NASA NTRS1979

Vertical profiles of CO and CH4 in the lower and middle troposphere over the Eastern United States January 1978

Samples of tropospheric air were obtained over the Eastern United States during January of 1978. These samples were analyzed by gas chromatography using flame ionization detection to produce vertical profiles of carbon monoxide and methane from the surface to 8 km. The carbon monoxide mixing ratios at 35 deg N and 45 deg N agree with previously published values; however, the mixing ratio at 25 deg N was significantly lower than most published values. The methane mixing ratio was weakly dependent on latitude and has an average value of 1.64 ppm.

Reichle, H. G., Jr.↗

NASA NTRS1978

Differential laser absorption monitoring of the atmosphere

In the airborne detection system of atmospheric constituents and pollutants described, double-ended differential absorption measurement is accomplished by rapidly current tuning the wavelength of a PbSSe diode laser across a single line of the species under consideration. As the laser wavelength sweeps periodically across the absorption line, the laser beam is amplitude modulated and is then synchronously detected. With this technique, a minimum detectable differential transmission of 0.02 percent is obtained for a 1-sec integration time.

Rubin, B.↗

NASA NTRS1978

DACOM - A rapid, high sensitivity airborne carbon monoxide monitor

A rapid, high sensitivity differential absorption carbon monoxide monitor (DACOM) has been developed to measure CO from an aircraft. The differential absorption measurement is accomplished by rapidly current tuning the wavelength of a PbSSe diode laser across a single 4.7 micron CO absorption line. As the laser wavelength sweeps periodically across the absorption line, the laser beam is amplitude modulated and is then synchronously detected. With this technique a minimum detectable differential transmission of 0.02% is obtained for a 1 second integration time. This performance is equivalent to a CO sensitivity of 5 ppb for a 10 meter absorption path. The techniques used to achieve this high sensitivity will be discussed. In the aircraft installation a 10 meter absorption path is located in the airstream along the fuselage of a C-54 aircraft. During flight tests of DACOM, a sensitivity of 20 ppb for a 1-second integration time has been achieved.

Sachse, G. W.↗

NASA NTRS1977

A measurement system for the atmospheric trace gases CH4 and CO

A system for measuring ambient clean air levels of the atmospheric trace gases methane and carbon monoxide is described. The analytical method consists of a gas chromatographic technique that incorporates sample preconcentration with catalytic conversion of CO to CH4 and subsequent flame ionization detection of these gases. The system has sufficient sensitivity and repeatability to make the precise measurements required to establish concentration profiles for CO and CH4 in the planetary boundary layer. A discussion of the bottle sampling program being conducted to obtain the samples for the concentration profiles is also presented.

Condon, E. P.↗

NASA NTRS1977

Three field tests of a gas filter correlation radiometer

Test flights to remotely measure nonurban carbon monoxide (CO) concentrations by gas filter correlation radiometry are discussed. The inferred CO concentrations obtained through use of the Gas Filter Correlation Radiometer (GFCR) agreed with independent measurements obtained by gas chromatography air sample bottle analysis to within 20 percent. The equipment flown on board the aircraft, the flight test procedure, the gas chromatograph direct air sampling procedure, and the GFCR data analysis procedure are reported.

Campbell, S. A.↗